Let’s understand Git Submodule

What is git submodule?

It is another git project inside your git repository. If you working on multiple git projects but need them in one repository instead. You will be happy to setup git submodule.

So here I have two git repositories for example:

https://github.com/muffat/repo-a
https://github.com/muffat/repo-b

And since I’m updating the repo-b frequently, I want my repo-b to be inside the repo-a so it helps me to work with multiple repos as possible and easy to maintain codes across the repo and be able to work more faster and efficiently.

Setup git submodule

Add git submodule in your current repo

$ git clone git@github.com:muffat/repo-a.git
$ cd repo-a/
/repo-a$
/repo-a$ git submodule add git@github.com:muffat/repo-b.git

Commit and push your submodule

/repo-a$ git add .
/repo-a$ git commit -m "Add submodule repo-b"
/repo-a$ git push origin master

Note that, git submodule doesn’t automatically get pulled after you clone your repository (repo-a). You need to do manual initialize and pull your submodule. So after you clone your repository, you will find out that your submodule directory (repo-b) is empty.

$ git clone git@github.com:muffat/repo-a.git
$ cd repo-a/
/repo-a$ cd repo-b/
/repo-a/repo-b/$ ls
/repo-a/repo-b/$

go to submodule directory, and do this:

/repo-a$ cd repo-b/
/repo-a/repo-b/$ git submodule init
/repo-a/repo-b/$ git submodule update

How to git clone including submodules

$ git clone --recursive git@github.com:muffat/repo-a.git

Some problem occurred whenever I tried to clone with recursive. It failed to fetch the submodule repository because of the permission. Although my submodule is a public repository, yet still failed.

Then I changed the url of submodule from git to be https.

$ cat .gitmodules
[submodule "repo-b"]
path = repo-b
url = https://github.com/muffat/repo-b.git
branch = master

After that, the git recursive cloning was working.

How to move your old repo to github

Before you begin, you might want to add your ssh key into your github account.

// push master branch
$ cd /repo-directory
$ git remote rename origin bitbucket
$ git remote add origin https://github.com/username/awesome-new-repo.git
$ git push origin master
$ git remote rm bitbucket

// push another branch
$ git checkout develop
$ git push origin -u develop

Arcanist cheatsheet

$ arc patch D123
$ git add .
$ git commit -am "update"
$ arc diff --update D123
$ arc land --revision D123

Update diff to master

$ git checkout master
$ git merge arcpatch-D123
$ git push

Make a diff from current working branch

$ git add.
$ git commit -am "update"
$ arc diff --update D123

Push to working branch without land

$ git add .
$ git commit -am "update"
$ git push origin lol-branch

Make a diff from working branch from the first update

$ git checkout lol-branch
$ git add.
$ git commit -am "update"
$ arc diff master

Git cheatsheet

list branch

git branch

rename branch

git branch -m <newname>

move to another branch

git checkout your-branch

hard reset branch

git reset --hard origin/master

create new branch

git checkout -b new-branch

delete local branch

git branch -D your-branch

merge from develop to master

git merge develop

init on existed project and push master for the first time

git init
git remote add origin ssh://git@bitbucket.org/your-username/your-repo.git
git add .
git commit -am "initial commit"
git push -u origin master